The present invention relates to data communication systems. More particularly, the present invention relates to the transmission of data through packet networks.
The current trend of using packet networks (PN) to transport data traditionally carried over circuit switched networks such as the Public Switched Telephone Network (PSTN) has created a need to support the installed-base of terminals attached to the PSTN. FIG. 1 illustrates a traditional PSTN environment as well as the interlace to a PN substitute network, as may be used with various customer premise equipment, such as telephones, fax machines, and modems.
The different nature between the two types of networks may be related to different operating characteristics such as bandwidth, delay, variations in delay, and loss of information, e.g., packet loss. The differences in characteristics between these networks can affect the terminals that have been designed with PSTN characteristics in mind, if and when those terminals need to communicate over a packet network. For example, many terminals are delay sensitive, and their interactive behavior with other components has been designed in consideration of the delay characteristics of the network in use at the time of their inception, typically, the PSTN. Further, it should also be appreciated that data communication networks need not exclusively include a packet network or a PSTN. For example, future networks may include portions of their infrastructure provided by one or the other type of network, as depicted in FIG. 2.
Hence, there is a need for the ubiquitous support of the installed-base of terminals on both networks. This support may involve the providing of new mechanisms to facilitate the communication of traditional devices over packet. networks. Support for these devices can depend on several factors, including the transported media characteristics, and thus can dictate the needs for a real-time infrastructure, such as voice communications, versus a non-real-time infrastructure, such as fax communications. Further, support for these devices can dictate the needs for a transparent support mode, i.e., one by which the actual data is transported transparently over the existing voice packet network infrastructure, versus a demodulation/remodulation support mode, where the information is demodulated, transported, and then remodulated.
As described above, the transport of data over a packet network may be subject to variation of delay, also known as jitter, as well as to packet loss characteristics, for example, during the establishment of a communication session, or during actual data transfer. Further, at the end of a communication session, once a terminal device decides to terminate a communication session, problems can occur in the tearing down of any remaining communication links. Accordingly, although some support mechanisms have been devised recently for the transport of voice and fax communications, a strong need exists for resolving various other issues relating to modem communication sessions, such as those related to the call numbering, establishment, transport and termination features.
The disclosed techniques for data communication may be employed with modems through a packet network. Further, the data communication techniques facilitate a virtual end-to-end connection between a first modem and a second modem such that the two modems can effectively behave as if directly connected to each other, unaware of any modifications to the data being transferred or to the protocols utilized within the communication connection. The above techniques can be carried out in a data communication system having, in addition to the modems, at least two gateways corresponding to the modems to facilitate the modem-to-modem communications through the packet network. During operation, the first modem will contact a corresponding first gateway regarding its intent to contact the second modem. After being contacted, the first gateway will suitably contact a second gateway corresponding to the second modem, which may establish a communication link between the second gateway and second modem. Additionally, negotiations can occur between the various gateways and modems to establish a communication session wherein the gateways can act in proxy for the two modems. Preferably, the communication system demodulates data coming from a first modem, transports the demodulated data in packets between the two gateways, and remodulates the data before delivering it to a second modem. Accordingly, data is transferred between the two modems through the virtual end-to-end communication connection.
In accordance with one aspect of the present invention, solutions for problems caused by the delays and the packet loss characteristics such as may be incurred for call establishment over a packet network, as well as for call numbering and calling options, are provided.
Further, in accordance with another aspect of the present invention, mechanisms such as end-to-end error detection, correction and re-transmission are provided to alleviate problems of flow control, such as variation of delay, i.e., jitter, and packet loss, which may occur during the transport of data over a packet network.
In accordance with yet another aspect of the present invention, solutions for facilitating termination at the end of a communication session are provided.